A developer transporting mechanism includes a pipe-like transporting path, sealing member, shutter, and urging member. The pipe-like transporting path, through which a developer is transported, has an discharge port at part of its side surface. The shutter is slidable along the surface of the sealing member to open and close the discharge port. The urging member urges the shutter in a direction in which the discharge port is closed. The sealing member is secured to the outer circumferential surface of the pipe-like transporting path. The sealing member also has a reduced part; its dimension in a width direction orthogonal to a direction in which the shutter moves is gradually reduced from the upstream end in the closing direction of the shutter toward the downstream end.